Tarrant was arrested on March 15 for his alleged involvement in the shooting deaths of 50 people at two mosques in Christchurch.
Tarrant will undergo mental health tests before his case proceeds. At times he looked around the room or cocked his head, seemingly to better hear what was being said.
The courtroom's public gallery was packed by about 50 friends and families of the victims, some staring quietly at the defendant throughout.
Friday's hearing is "likely to be relatively brief", Justice Mander said.
It is unknown, however, whether Mr Tarrant will be the first person to be charged under the anti-terror laws of New Zealand.
"I$3 just want to see what he has to say, what sort of feeling he's got [his] emotion, to see what his reaction is, good or bad and the truth will come out of him", Yama Nabi told RNZ before this morning's court hearing.
Armed officers continue to guard the justice precinct - including the courthouse - in central Christchurch, but the proceedings on Friday were open to the public, with some family members who lost loved ones in the shootings in attendance.
The media will be allowed to attend the hearing, but the judge has denied access to film, photograph and recordings at the hearing.
However, the charges were updated Friday to include the names of all 50 who were killed in the attack and 39 others who were wounded.
Police said further charges were being considered against Tarrant - a self-avowed white supremacist - but did not specify what they were.
Criminal charges, such as murder and attempted murder are easier to pursue, although prosecutors may want the accused tried as a terrorist to make the point that right-wing extremism is just as risky as its Islamic counterpart.
Thousands of written submissions on the changes have already been received, including strong pushback from some parts of the hunting and gun enthusiast community. A regular at one of the mosques, Alam was not there during the attack.
However, two Auckland lawyers, Shane Tait and Jonathan Hudson, appeared in court on his behalf.
Tarrant's second court appearance comes three weeks after the attack, as the New Zealand government rushed to make changes to gun laws and investigate how he was able to carry out the attacks.